Method of urinalysis, urinalysis apparatus, method of measuring angle of rotation and polarimeter

ABSTRACT

The present invention provides a urinalysis apparatus easy to maintain and manage without using any supplies such as the test paper, in which the concentration of an optically active substance in urine is determined by measuring the angle of rotation of the urine. Also, a polarimeter and a urinalysis apparatus which are reliable, compact and inexpensive are provided by using a polarimeter including means for transmitting the polarized light through a specimen, applying a magnetic field to the specimen and detecting the change in the direction of light polarization due to the application of the magnetic field.

TECHNICAL FIELD

The present invention relates to a method of measuring an angle ofrotation usable for identifying, examining a purity and determining aconcentration of a solute in the solution, and a polarimeter using themethod, and more particularly to a method and an apparatus forurinalysis in which the angle of rotation of urine sampled from a man orother animal for examining the concentration of glucose, protein, etc.contained in the urine.

BACKGROUND ART

A healthy adult person usually voids 1000-1500 ml of urine every day.The total amount of solid components thereof is 50-70 g. About 25 g ofthe solid components is inorganic substances mainly composed of sodiumchloride, potassium chloride and phosphoric acid, most of which aredissolved in the form of ions. The remains are organic substances mainlycomposed of urea and uric acid, and slight amounts of sugar and proteinalso exist therein. The concentrations of sugar and protein in the urinereflect the health conditions of the adult.

The sugar contained in the urine, i.e., glucose is discharged usually ata rate of 0.13-0.5 g per day into the urine. From this figure and theamount of urine, the concentration, i.e., the urine glucose level can beestimated at not more than 50 mg/dl on the average. The correspondingvalue is several hundred mg/dl, or sometimes as high as several thousandmg/dl. In other words, the value for diabetics can increase by a factorof ten or hundred as compared with the normal value.

On the other hand, the protein contained in urine, i.e., albumin issmaller in amount than glucose, and discharged at the rate of 3-60 mginto the urine. By taking the amount of the urine into account, averageconcentration is about 6 mg/dl or less. If a kidney is suffered, thealbumin concentration reaches 100 mg/dl or more. That is, the value isincreased to ten times the normal value or more.

Ordinally, as a conventional method of examining such sugar or proteinin the urine, a test paper impregnated with an agent is dipped into theurine and a color reaction thereof is measured by spectrophotometer orthe like.

In this method, however, different kinds of test paper were required touse for different items of examination including sugar, protein, etc.Also, a new test paper is required for each test, thereby leading to thedisadvantage of a high running cost. Further, automation for laborsaving has its own limit.

In addition, in a case of home use, a layman is demanded to set andchange the test paper. This process is comparatively annoying and formsa stumbling block to the extension of the domestic use of the urinalysisapparatus.

Now, the conventional polarimeter will be explained. The conventionalpolarimeter had the problems described below.

An example of the conventional polarimeter is shown in FIG. 20.

In FIG. 20, a light source 121 is configured of a sodium lamp, aband-pass filter, a lens, a slit, etc. for projecting a substantiallyparallel light composed of a sodium D ray having a wavelength of 589 nm.A polarizer 122 is arranged in the direction of advance of the lightprojected from the light source 121 in such a position as to transmitonly a component in a specific direction, which has a plane of vibrationcoincident with a transmission axis thereof, of the light projected fromthe light source 121. A sample cell 123 for holding a specimen isarranged in the direction of advance of the light transmitted throughthe polarizer 122. Further, an analyzer 124 is arranged, like thepolarizer 122, in such a position as to transmit only the component ofthe light in a specific direction. An analyzer rotator 125 is forrotating the analyzer 124 on an axis parallel with the direction ofadvance of the light projected from the light source 121 under thecontrol of a computer 127. A light sensor 126 is for detecting the lightprojected from the light source 121 and transmitted through thepolarizer 122, the sample cell 123 and the analyzer 124. The computer127 controls the analyzer rotator 125 while recording and analyzing asignal from the light sensor 126.

The principle of this conventional example will be explained withreference to FIG. 21. In the figure the abscissa represents the relativeangle θ formed between the plane of vibration of the light transmittedthrough the polarizer 122 and the plane of vibration of the lighttransmitted through the analyzer 126. Herein, θ is assumed to take zerowhen the angle between these two planes of vibration reaches π/2, i.e.,in the orthogonal nicol state. The ordinate represents an intensity I ofthe light that has reached the light sensor 126 based on an outputsignal of the light sensor 126. Herein, the solid line indicates theoutput signal in the case where the specimen exhibits no opticalrotatory power. Under this condition, the relation between θ and I isshown by equation (1) mentioned below. Herein, a transmission loss and areference loss of the s ample cell 123 and the analyzer 122 respectivelyare ignored.

    I=T×I.sub.O ×(cos θ).sup.2               (1)

where,

T: transmittance of specimen

I_(O) : intensity of light incident to specimen

As apparent from equation (1), I changes with a change of θ, i.e., withthe rotation of the analyzer 126, so that an extinction point with aminimum I appears for each π.

In the case where the specimen has an optical rotatory power and itsangle of rotation=α, on the other hand, the light intensity isrepresented by dashed line in FIG. 21 and given by equation (2).

    I=T×I.sub.O ×{cos(θ-α)}.sup.2      (2)

As seen from this, a specimen having an optical rotatory power, ascompared with a specimen having no optical rotatory power, has the angleassociated with the extinction point displaced by α. The angle ofrotation can be measured by finding the displacement α of the angleassociated with the extinction point by the computer 127.

In this method, however, S/N ratio of the output signal of the lightsensor 126 is comparatively inferior for lack of a modulated componentand it is difficult to accurately determine the extinction point. As aresult, a specimen with a small α cannot be measured with high accuracy.

For this reason, a polarimeter shown in FIG. 22 is also used in order toimprove an accuracy of determining the extinction point. In FIG. 22, alight source 141 is configured of a sodium lamp, a band-pass filter, alens, a slit, etc. for projecting a substantially parallel light ofsodium D ray having a wavelength of 589 nm. A polarizer 142 and ananalyzer 144 are arranged in the direction of advance of the lightprojected from the light source 141 aligning their transmission axeswith the direction of advance of the light projected from the lightsource 141, with a sample cell holding a specimen interposedtherebetween. An analyzer rotator 145 is for rotating the analyzer 144on the transmission axis thereof as a rotation shaft under the controlof a computer 147. A light sensor 146 detects the light projected fromthe light source 141 and transmitted through the polarizer 142, thesample cell 143 and the analyzer 144. The computer 147 controls theanalyzer rotator 145, and records and analyzes the signal of the lightsensor 146. An optical Faraday modulator 151 vibrates the direction ofpolarization. A signal generator 152 drives the optical Faradaymodulator 151. A lock-in amplifier 143 is for phase sensitive detectionof an output signal of the light sensor 146 with reference to thevibration-modulated signal from the optical Faraday modulator 151.

The operating principle of the polarimeter will be explained below withreference to FIG. 23.

In FIG. 23, the abscissa and the ordinate represent, as same in FIG. 21,θ and I, respectively, with the extinction point and the neighborhoodthereof shown in an enlarged view. The optical Faraday modulator 151vibration-modulates the direction of polarization with an amplitude of δand an angular frequency of ω. In the process, I is given as shown inequation (3) below from equation (2).

    I=T×I.sub.O ×{cos(θ-α+δ×sin(ω×t))}.sup.2(3)

where

t: time

In FIG. 23, the extinction point or the neighborhood thereof isinvolved, i.e., θ≈π/2, and therefore equation (4) can be approximated asshown by equation (4).

    θ≈π/2+β                              (4)

where,

|β|<<1

Substituting this equation (4) into equation (3) gives equation (5)below.

    I=T×I.sub.O ×{[sin(β-α+δ×sin(ω×t)]}.sup.2(5)

If it is assumed that an angle of rotation of the specimen and anamplitude of vibration. modulation are small, that is |α|<<1 and δ<<1,equation (5) is approximated as shown in equation (6) below.

    I≈T×I.sub.O ×{β-α+δ×sin(ω×t)}.sup.2

    =T×I.sub.O ×{(β-α).sup.2 +2×(β-α)×δ×sin(ω×t)+[.delta.×sin(ω×t)].sup.2 }

    =T×I.sub.O ×{(β-α).sup.2 +2×(β-α)×δ×sin(ω×t)+[.delta..sup.2 /2×(1-cos(2×ω×t))]}        (6)

This indicates that the output signal I of the light sensor containssignal components of angular frequency=O (DC), ω and 2×ω. This isobvious also from FIG. 15. By the phase sensitive detection of the valueI with the vibration-modulated signal as a reference signal in thelock-in amplifier, it is possible to pick up the component of theangular frequency ω, i.e., the value S shown in equation (7) below.

    S=T×I.sub.O ×2×(β-α)×δ(7)

This S is zero only when β=α and this point constitutes an extinctionpoint. In other words, the value of β when S becomes zero in a step ofrotating the analyzer and sweeping β is the angle α of rotation.

As described above, modulation of the direction of polarization, makesit possible to pick up the signal of the modulated frequency componentselectively by separating it from noises such as a source lightintensity, power fluctuations and radiation, thereby making it possibleto obtain the signal S with high S/N. This value S can be used todetermine the extinction point accurately and permits a highly accuratemeasurement of the angle a of rotation.

Nevertheless, the above-mentioned polarimeter is complicated instructure due to the need of a means for rotating the analyzer and amodulator, and therefore has its own limit of cost reduction andreliability.

DISCLOSURE OF INVENTION

Taking these subjects into consideration, the object of the presentinvention is to provide a method of urinalysis easy to maintain andmanage without using supplies such as a test paper. Further, the objectof the present invention is to provide a reliable, compact andinexpensive polarimeter and a urinalysis apparatus using this one.

According to the method of urinalysis of the present invention, aconcentration of an optically active substance contained in urine isdetermined by measuring an angle of rotation of the urine. Glucose andprotein existing in the urine exhibit an optical rotatory power whereasurea and uric acid constituting the main components of the organicsubstances in the urine have no optical rotatory power. Also, none ofthe inorganic substances in the urine exhibits the optically rotatorypower. For this reason, the concentration of glucose or protein in theurine can be accurately determined by measuring the angle of rotation ofthe urine. Similarly, the concentration of L-ascorbic acid (what iscalled vitamin C) which may be contained in the urine can also bedetermined by measuring the angle of rotation. Once the angle ofrotation of the urine is measured by using a high-precision polarimeter,therefore, the angle of rotation due to the optically active substanceslike glucose and protein existing in low concentration can be detectedthereby making it possible to calculate the concentration of thesesubstances. As a result, the concentration of the glucose and protein inthe urine can be examined without using any supplies.

The present invention provides a highly accurate, reliable, compact andinexpensive polarimeter which solves the above-mentioned problems of theconventional polarimeter.

The principle of a method of analyzing the urine by measuring the angleof rotation according to the invention will be explained below.

The angle A of rotation is proportional to the product of a specificangle a of rotation and the concentration C of an optically activesubstance. This relation is shown by equations (8) and (9).

In the case where only one type of optically active substance isinvolved, the relation is given by

    A [degree]=L [cm]×α×C [kg/dl]            (8)

while if N types of optically active substances are contained, therelation holds:

    A=L×(α.sub.1 ×C.sub.1 +α.sub.2 ×C.sub.2 . . . +α.sub.N ×C.sub.N)                            (9)

where L is the measured optical path length.

The specific angles a of rotation of glucose and albumin are shown inTable 1.

                  TABLE 1                                                         ______________________________________                                        wavelength       589 nm  580 nm                                               ______________________________________                                        glucose            50      25                                                 albumin          -60     -10                                                  ______________________________________                                         Unit: [degree/cm·dl/kg                                          

The specific angles of rotation shown above are values for a glucoseaqueous solution and an albumin aqueous solution at 20° C.

Specifically, when a light having a wavelength of 589 nm propagates bythe distance of 10 cm through the glucose aqueous solution of 100 g/dlin concentration, a direction of polarization of the light rotates by 50degrees. Although this concentration cannot be achieved due to thelimited solubility of glucose actually, the direction of polarizationrotates by 50×10⁻³ degrees at the concentration of 100 mg/dl since theangle of rotation and the concentration are in proportion as shown inequation (8).

In the case where glucose is the only optically active substance in theurine, therefore, a urine glucose level can be calculated from thespecific angle of rotation of glucose by measuring the angle of rotationof the urine. A similar calculation is possible also for albumin andL-ascorbic acid.

Further, an angle of rotation of urine having a known range of angle ofrotation presented by an interfering optically active substance otherthan optically active substance of unknown concentration is measured,and the concentration C of the optically active substance is determinedto be within the range of

    (A-A.sub.h)/(α×L)≦C≦(A-A.sub.l)/(α×L)(10)

where

A: measured angle of rotation of the urine [degree],

A_(h) : maximum value of the angle of rotation presented by theinterfering optically active substance [degree],

A_(l) : minimum value of the angle of rotation presented by interferingoptically active substance [degree],

α: specific angle of rotation of the optically active substance[degree/cm·dl/kg], and

L: measurement optical path length [cm].

According to this method, the concentration of each of a plurality ofoptically active substances including glucose, albumin, L-ascorbic acid,etc., which may coexist in urine can be calculated.

First, equation (9) is modified to obtain equation (11) below.

    A=A.sub.x +A.sub.d                                         (11)

where it is assumed that

    A.sub.x =L×α.sub.1 ×C.sub.1, and

    A.sub.d =L×(α.sub.2 ×C.sub.2 + . . . +α.sub.N ×C.sub.N).

In equation (2), assume that substance 1 is an optically activesubstance X to be detected, and substances 2-N are other opticallyactive substances, i.e., interfering optically active substances, A_(d)corresponds to the angle of rotation presented by the interferingoptically active substances. If the concentration range of thesubstances 2 to N is known, the maximum value A_(h) and the minimumvalue A_(l) that A_(d) can assume are known. This leads to equation (12)below.

    A-A.sub.h ≦A.sub.x =A-A.sub.d ≦A-A.sub.1     (12)

Equation (12) determines the range of the angle A_(x) of rotation, andthe concentration C_(x) is also determined from the specific angle α_(x)of rotation and the length L of the measurement optical path. Equation(12) is expressed as equation (10) in terms of the concentration C ofthe optically active substance X.

In the case where the glucose concentration in urine is examined, forexample, assume that the concentration of the interfering albumin is notmore than 10 mg/dl, i.e., assume that the minimum value of the albuminconcentration which can be assumed is 0 and the maximum value thereof is10 mg/dl, respectively, with the wavelength of 589 nm and the length ofmeasurement light path of 10 cm, A_(h) is zero degree and A₁ is -6×10⁻³degrees. Then, assuming that measurement A=0.1 degree, the glucoseconcentration C (mg/dl) can be determined to be 200≦C≦212 from Table 1.

Actually, considering the fact that an abnormal urine glucose level canreach not less than several hundred mg/dl, the examination with theabove-described accuracy often suffices. Specifically, in the case wherethe albumin concentration is about 10 mg/dl or less representing anormal value, the abnormality of the sugar in the urine can bedetermined by measuring the angle of rotation with a single wavelength.

Further, angles of rotation of the urine including N types of opticallyactive substances is measured using the light having N different typesof wavelength thereby to determine the concentrations of the opticallyactive substances in the urine. The specific angle of rotation varieswith wavelength due to optically rotatory dispersion. Consequently, inthe case where N types of optically active substances coexist, Nindependent simultaneous equations can be obtained using equation (9) bymeasuring the angle of rotation by each of the N wavelengths. This makesit possible to calculate the concentration for N types of opticallyactive substances.

In this way, the abnormality of the sugar or the albumin concentrationin the urine can be determined by measuring the angle of rotation of theurine.

Also, the angle of rotation of the urine for the light having awavelength of not less than 500 nm is measured. For the short wavelengthof less than 500 nm, the absorption due to urochrome (a yellow componentof urine), principally, increases to such an extent that the measurementaccuracy is sometimes adversely affected.

Further, the concentration of a light-scattering substance contained inthe urine is determined by measuring an amount of a light scattered inthe urine.

Also, the light scattering substance is at least one of protein andblood. The molecular weight of the albumin constituting protein in theurine is about 70 thousands, which causes light scattering sufficientlylarge as compared with the light scattering due to the molecular weightof other organic substances including glucose (having a molecular weightof about 180) or the like and inorganic substances contained in theurine. Specifically, the scattering of the light propagating in theurine is dominated by albumin. As a result, the albumin concentrationcan be determined by irradiating light to the urine and observing thescattered light directly or in the form of the decreasing amount of thetransmitted light. It is also possible to examine the presence orabsence of the blood which have comparatively large particles.

Further, the amount of the scattered light in the urine is measured forthe light having a wavelength of not less than 500 nm. As in the case ofmeasuring the specific angle of rotation, the light having a wavelengthof shorter than 500 nm involves an increased absorption mainly due tourochrome, often adversely affecting the measurement accuracy.

Furthermore, the amount of the scattered light is measured together withthe angle of rotation of the urine thereby to determine theconcentration of the light scattering substances as well as theoptically active substances contained in the urine. This is effectiveespecially in the case where both glucose and albumin exist in an amountnot negligible in the urine.

In this way, according to the present invention, the concentration ofsugar and protein in the urine can be easily and accurately determinedby measuring the angle of rotation of the urine. This method alsoeliminates the need of supplies such as the test paper unlike in theprior method.

In addition, a high reliability and a low cost of the polarimeter ismade possible, and a reduced cost and a higher reliability of theurinalysis apparatus is also made possible as described below.

According to the method of measuring the angle of rotation of thepresent invention, an angle of rotation of a specimen is measured byapplying a magnetic field to the specimen and detecting the change inthe direction of polarization of the light due to the magnetic field.

In view of this, the present invention provides a polarimeter comprisinga monochromatic light source for projecting the light, a polarizer fortransmitting only the polarized component in a specific direction of theprojected light, a sample cell for holding the specimen and arranged insuch a manner that the light passed through the polarizer is transmittedthrough the specimen, means for applying a magnetic field to thespecimen, means for sweeping the magnetic field, an analyzer fortransmitting only the polarized component in a specific direction of thelight transmitted through the specimen, a light sensor for detecting thelight transmitted through the analyzer, and calculation means forcalculating an angle of rotation of the specimen on the basis of amagnetic field sweep signal of the magnetic field sweeping means and anoutput signal of the light sensor.

When a light is propagated through a medium and a magnetic field isapplied in the direction of propagation of the light, the direction ofpolarization of the light is rotated in accordance with the propagation.This phenomenon is called the optical Faraday effect. This opticalFaraday effect is given by equation (13) below.

    a=V×H×L                                        (13)

where

a: rotational angle of the direction of polarization [minute],

V: Verdet's constant of the medium [minute/A],

H: magnetic field [A/m], and

L: propagation distance [m].

The value V in equation (13) is varied with the medium, light wavelengthand temperature. An example of V for various media is shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                    V/100 [minute/A]                                                  ______________________________________                                        water          1.645                                                          chloroform    2.06                                                            acetone       1.42                                                            rock crystal   2.091                                                          flint glass   4.85                                                            ______________________________________                                         Temperature = 20° C.                                                   Wavelength = 589 nm                                                      

This optical Faraday effect is utilized by the optical Faraday modulatorused in the prior art. This is such that a solenoid coil is wound on arod of flint glass and is supplied with a current to apply a magneticfield thereto, thereby modulating the direction of polarization of thelight propagated in the direction of the magnetic field. Free modulationcan be conducted by controlling the current flowing in the solenoidcoil.

As described above, the optical Faraday effect permits the modulation ofthe polarization direction upon application of a magnetic field to amedium. As apparent from Table 2, this is also the case with water,chloroform, acetone or the like widely used as a solvent. Therefore,upon application of a magnetic field to a solution with a specimendissolved therein, the very solution rotates the direction ofpolarization of the light propagating through the solution by theoptical Faraday effect. Specifically, once a magnetic field is appliedto a sample cell holding a specimen, the particular sample cell and themagnetic field application means function as an optical Faradaymodulator. A solenoid coil, a magnet etc. which apply the magnetic fieldin the direction of light propagation can be used as a magnetic fieldapplication means. The magnetic field can be modulated by modulating thecurrent flowing in the solenoid coil or by modulating the distancebetween the magnet and the specimen. In this way, the direction ofpolarization can be vibration-modulated by vibration-modulating themagnetic field, thereby making it possible to measure the angle ofrotation in the same manner as in the prior art.

Also, if the magnetic field is swept, i.e., if the applied magneticfield is changed from a given strength to a different strength(including a change in polarity of the magnetic field), then thedirection of polarization of the magnetic field can be rotated. By doingso, the same effect can be obtained as if the analyzer is rotated.Specifically, unlike in the prior art in which the displacement of theextinction point with the rotation of the analyzer is directly read fromthe angle of the analyzer, the method of measuring the angle of rotationaccording to the present invention is such that the displacement of theextinction point with the magnetic field swept is read by a currentvalue, for example, which is converted into a magnetic field and furtherinto an angle, thereby measuring the angle of rotation of the specimen.This is substantially the same as if a magnetic field is detected inwhich the angle of rotation generated by an optically active substanceof a specimen coincides with the rotational angle of the direction ofpolarization due to the optical Faraday effect caused by an applicationof the magnetic field.

Sweeping of the magnetic field is not necessarily limited to acontinuous change of strength but includes a discrete change thereof. Inview of the fact that a change in the characteristic of an output signalof a light sensor with the rotation of the direction of polarization isgenerally known, the angle of rotation can be calculated by measurementstaken at two or more points and interpolation or extrapolation from themeasurements. Specifically, the angle of rotation of a specimen can becalculated from the output signals of the light sensor for at least twodifferent magnetic fields. In such a case, the measurement time can beshortened.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a polarimeterused in an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relation between aglucose concentration of an aqueous solution of glucose or urine withglucose dissolved therein and an angle of rotation obtained by ameasurement using the same polarimeter.

FIG. 3 is a schematic diagram showing a configuration of a polarimeterused in another embodiment of the present invention.

FIG. 4 is a characteristic diagram showing the relation between aglucose concentration of glucose aqueous solution or an albuminconcentration of an albumin aqueous solution and the angle of rotationfor the light having a wavelength of 830 nm obtained by a measurementusing the same polarimeter.

FIG. 5 is a characteristic diagram showing a relation betweenconcentrations of the same aqueous solutions and angles of rotation fora light having a wavelength of 589 nm.

FIG. 6 is a schematic diagram showing a configuration of a scatteredlight amount measuring instrument used in another embodiment of thepresent invention.

FIG. 7 is a characteristic diagram showing a relation between aconcentration of an albumin aqueous solution and a scattered lightamount obtained by using the same measuring instrument.

FIG. 8 is a characteristic diagram showing a relation between awavelength of the incident light and an intensity of a light transmittedthrough the urine.

FIG. 9 is a schematic diagram showing a configuration of a polarimeterused in another embodiment of the invention.

FIG. 10 is a characteristic diagram showing a relation between theamount of the current flowing in a solenoid coil and an output signal ofthe light sensor obtained by using the same polarimeter.

FIG. 11 is a characteristic diagram showing a relation between aconcentration of an aqueous solution of cane sugar and the output signalof the light sensor obtained by using the same polarimeter.

FIG. 12 is a schematic diagram showing a configuration of a polarimeteraccording to still another embodiment of the present invention.

FIG. 13 is a characteristic diagram showing a relation between a currentamount J supplied to the solenoid coil and an output signal of a lock-inamplifier obtained by using the same polarimeter.

FIG. 14 is a characteristic diagram showing a relation between aconcentration of an aqueous solution of cane sugar and an output signalof the light sensor obtained by using the polarimeter.

FIG. 15 is a characteristic diagram showing a relation between a glucoseconcentration of a glucose aqueous solution or a urine with glucosedissolved therein and an angle of rotation obtained by a measurementusing the polarimeter.

FIG. 16 is a schematic diagram showing a configuration of a polarimeteraccording to still further embodiment of the present invention.

FIG. 17 is a schematic diagram showing a configuration of a polarimeteraccording to yet still further embodiment of the present invention.

FIG. 18 is a schematic diagram showing a configuration of a polarimeteraccording to a further embodiment of the present invention.

FIG. 19 is a characteristic diagram showing the relation between astandardized variable X and a concentration of an aqueous solution ofglucose obtained by using the polarimeter.

FIG. 20 is a schematic diagram showing a conventional polarimeter.

FIG. 21 is a characteristic diagram showing a relation between arotational angle θ and a detected light intensity based on the principleof measurement of the polarimeter.

FIG. 22 is a schematic diagram showing another polarimeter.

FIG. 23 is a characteristic diagram showing the relation between therotational angle θ and the detected light intensity based on theprinciple of measurement of the polarimeter.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the invention will be described below indetail.

<<Embodiment 1>>

A first embodiment will be explained in detail below.

FIG. 1 is a diagram showing a configuration of a polarimeter used in thepresent embodiment. The basic principle of this polarimeter is theoptical zero-order method based on the vibration of the plane ofpolarization using the Faraday effect.

A low-pressure 180 W sodium lamp 1 emits a parallel light. A band-passfilter 2 transmits only the components having a wavelength of 589.0 nmof the light emitted from the sodium lamp 1. A polarizer 3 passesspecific component of the polarized light from the band-pass filter 2which have a plane of vibration parallel to the page, for example. Amodulated signal current input from a Faraday cell driver 5 causes theFaraday cell 4 to modulate the direction of polarization of thetransmitted light by a very small width due to the optical Faradayeffect. The substantial length of the light path of a sample cell 6 forcontaining the urine is 10 cm. A rotary analyzer 7, like the polarizer3, passes only specific polarized component of the light transmittedthrough the sample cell 6, but can be set at an arbitrary angle by ananalyzer driver 8. A light sensor 9 detects the light transmittedthrough the rotary analyzer 7 and outputs a signal based on theintensity of the light thus detected. A lock-in amplifier 10 subjectsthe output of the light sensor 9 to phase sensitive detection with themodulated signal applied to the Faraday cell 4 as a reference signal. Acomputer 11 applies to the analyzer driver 8 an instruction forcontinuously rotating the rotary analyzer 7 while recording the outputof the lock-in amplifier 10. As a result, the angle of the rotaryanalyzer 7 at which the output of the lock-in amplifier 10 becomes zerois found to calculate the angle of rotation. With the above-mentionedconfiguration, the accuracy of about 10⁻³ is achieved.

The urine was analyzed as described below using this polarimeter.

First, in order to confirm the performance of the polarimeter, ananalytical curve was plotted as described below. Pure water was placedinto a sample cell 6, and the angle of the rotary analyzer 7 wasmeasured at which the output of the lock-in amplifier 10 becomes zero.At this time, the polarizer 3 and the rotary analyzer 7 are in theorthogonal nicol state. With this angle as a reference and with the purewater as a solvent, the angle of rotation was measured of glucoseaqueous solutions prescribed with concentrations of 20, 100, 200, 300and 500 mg/dl, respectively. The result is shown by white circles inFIG. 2. This indicate that the glucose concentration can be measured.

Then, the angle of rotation was measured of the urine determined to havea glucose concentration of 50 mg/dl or less and an albumin concentrationof 10 mg/dl or less by the urinalysis made in advance using the testpaper. Further, with this urine as a solvent, glucose solutions havingconcentrations of 20, 100, 200, 300 and 500 mg/dl, respectively, inother words, artificial glycosuria were prepared, and the angle ofrotation of these were measured. The result is shown by black circles inFIG. 2. The angle of rotation of these artificially-prepared glycosuriais represented by a straight line translated in parallel from theanalytical curve by 1.5×10⁻² degrees and accurately reflects the glucoseconcentrations.

The angle of rotation of the urine itself was 1.5×10⁻² degrees. This,combined with the range of albumin concentration obtained in advance byurinalysis, can decide from equation (10) the glucose concentration C as

    30 mg/dl≦C≦42 mg/dl

This coincides with the result of analysis obtained beforehand.

Further, the angle of rotation was measured similarly of the urinedetermined by an urinalysis apparatus to have a glucose concentration of30 mg/dl or more and a normal albumin concentration, i.e., 10 mg/dl orless. As a result, this urine exhibited the angle of rotation of2.2×10⁻¹ degrees. This, combined with the range of albumin concentrationobtained in advance by the urinalysis apparatus, shows that the glucoseconcentration C is

    440 mg/dl≦C≦452 mg/dl

This also coincides with the result of analysis obtained in advance.

In this way, for the urine having a normal albumin concentration, anabnormal glucose concentration of the urine (urine glucose level) can beaccurately detected by measuring the angle of rotation. For example, theglucose concentration of 300 mg/dl or more can be determined with anerror of about 12 mg/dl.

As described above, according to this embodiment, the urine glucoselevel can be examined without using any supplies such as test paper,thereby greatly contributing to practical effects.

<<Embodiment 2>>

Explanation will be made about a method of analyzing the urinecontaining both glucose and albumin in an amount not negligible.

According to this embodiment, a polarimeter shown in FIG. 3 was usedtogether with the polarimeter shown in the first embodiment. Thispolarimeter, like the polarimeter of the first embodiment, operates onthe basic principle of the optical zero-order method based on thevibration of the plane of polarization using the Faraday effect.Numerals 3 to 11 designate the same components as the corresponding onesused in the first embodiment. But, a semiconductor laser light source 12was used in place of the sodium lamp. The semiconductor laser lightsource 12 projects a parallel light of 5 mW having an emissionwavelength of 830 nm. This polarimeter operates in the same manner asthe corresponding one of the first embodiment and achieved the accuracyof about 10⁻³ degrees.

First, in order to confirm performance of this polarimeter, ananalytical curve was prepared. With pure water placed in a cell, theangle of the rotary analyzer 7 was measured at which the output of thelock-in amplifier 10 becomes zero. On the other hand, glucose aqueoussolutions having concentrations of 20, 100, 200, 300 and 500 mg/dl,respectively, and albumin aqueous solutions having concentrations of 20,50 and 100 mg/dl, respectively, were prepared. With the angle of theanalyzer for the pure water as a reference, the angle of rotation ofthese aqueous solutions were measured. The result is shown in FIG. 4.This indicates that the angle of rotation thus measured can beapproximated linearly with respect to the concentration of glucose oralbumin. In other words, it was confirmed that the concentration ispossible to measure.

Then, the same specimens were measured by a polarimeter using a lightsource having a wavelength of 589 nm as in the first embodiment. Theresult is shown in FIG. 5.

Equation (9) and the specific angles of rotation in Table 1 givesimultaneous equations shown in equations (14) and (15). Let the glucoseand albumin concentrations be C₁ and C₂ [kg/dl], respectively:

    A.sub.589 =0.1×(50C.sub.1 -60C.sub.2)                (14)

    A.sub.830 =0.1×(25C.sub.1 -10C.sub.2)                (15)

where

A₅₈₉ : angle of rotation [degrees] for the light having a wavelength of589 nm, and

A₈₃₀ : angle of rotation [degrees] for the light 830 nm in wavelength.Measurement of A₅₈₉ and A₈₃₀ makes possible calculation of two unknownfigures C₁ and C₂ from equations (14) and (15), respectively.

In fact, an aqueous solution containing 100 mg albumin and 300 mgglucose per dl was prepared and the angle of rotation of this aqueoussolution was measured in the same manner. The result was

    A.sub.589 =9.0×10.sup.-2 [degrees]

    A.sub.830 =6.5×10.sup.-2 [degrees]

The simultaneous equations (14) and (15) were solved using this result,and it was confirmed that the result coincides with the loading ratiobetween albumin and glucose.

In similar fashion, the angle of rotation was measured of the urinewhich had been decided to have a glucose concentration of 50 mg/dl orless and an albumin concentration of 100 mg/dl or more as a result ofthe conventional urinalysis using the test paper. The measurement showsthat the angle of rotation A₅₈₉ for the wavelength of 589 nm and theangle of rotation A₈₃₀ for the wavelength of 830 nm were

    A.sub.589 =-6×10.sup.-2 [degrees]

    A.sub.830 =-5×10.sup.-3 [degrees]

Equations (14) and (15) were solved using this result thereby to obtaina glucose concentration of 30 mg/dl and an albumin concentration of 125mg/dl. This coincides with the result of the conventional urinalysis.

Also, the angle of rotation was measured of the urine which had beendecided to have a glucose concentration of 300 mg/dl or more and analbumin concentration of 100 mg/dl or more. As a result, the angles ofrotation A₅₈₉ and A₈₃₀ were determined as

    A.sub.589 =1×10.sup.-1 [degrees]

    A.sub.830 ==8×10.sup.-2 [degrees]

Equations (14) and (15) were solved using this result thereby to obtaina glucose concentration of 380 mg/dl and an albumin concentration of 150mg/dl. This coincides with the result of the conventional urinalysis.

As described above, according to this embodiment, in the case where bothglucose and albumin exist in the urine to an extent not negligible, theurine glucose level and the albumin concentration thereof can beexamined without using any supplies such as the test paper bydetermining the angles of rotation using a plurality of light havingdifferent wavelengths.

<<Embodiment 3>>

In this embodiment, a method will be explained for examining the albuminconcentration in the urine and a bloody urine by the light scatteringaction.

A urinalysis apparatus according to this embodiment will be explainedbelow with reference to FIG. 6.A helium neon laser 13 is adapted toproject parallel light 5 mW in output having a wavelength of 633 nm ontoa sample cell 14 containing the urine. The sample cell 14 has asubstantial light path length of 10 cm and a width of 1 cm. Since thesample cell 14 has the two transparent sides, a scattered light indirection perpendicular to the light path can pass outward of the samplecell 14. A light sensor 15 is arranged with the angle of visibilitythereof coinciding with the sample cell 14 and capable of detecting thescattered components of the laser light propagating in the urine.

Albumin aqueous solutions of 20, 50 and 100 mg/dl in concentration,respectively, were prepared, and the scattered light amount of thesesolutions and pure water were measured. The result is shown in FIG. 7.In this way, a positive correlation was confirmed between the albuminconcentration and the scattered light amount.

Then, the scattered light amount was measured of the urine that had beendecided to have a glucose concentration of 50 mg/dl or less and analbumin concentration of 10 mg/dl or less by the analysis using the testpaper, but the scattered light could not be detected. A measurement ofthe urine that had been decided to have a glucose concentration of 300mg/dl or more and an albumin concentration of 10 mg/dl or more by theconventional urinalysis method, on the other hand, confirmed thepresence of a signal of about 6 on the scale in FIG. 7. Further, asignal of about e could also be confirmed by another measurement of anurine that had been decided to have a glucose concentration of 50 mg/dlor less and an albumin concentration of 100 mg/dl or more by theconventional urinalysis method. In the process, the scattered lightamount was measured on an arbitrary scale.

As described above, the albumin concentration can be determined bymeasuring the amount of the scattered components of the lightpropagating in the urine. In this way, scattering of the light due tocomparatively large particles such as albumin or blood is sufficientlylarge as compared with the scattering of the light due to glucose orother organic or inorganic substances in the urine. In other words,scattering of the light propagating in the urine due to albumin andblood is controlling. Consequently, it is possible to determine thealbumin concentration or the blood concentration in the urine byirradiating light into the urine and observing the amount of scatteredlight.

As explained above, according to this embodiment, the presence of largeparticles such as albumin and blood can be examined without using anysupplies like the test paper, thereby greatly contributing to practicaleffects.

<<Embodiment 4>>

In this embodiment, a method of urinalysis will be explained in whichboth an angle of rotation and an amount of scattered light propagatingin urine are measured at the same time. This examination method iseffective especially in the case where the amounts of glucose andalbumin existing in urine are both not negligible. Also, according tothis embodiment, unlike in the third embodiment, the scattered lightamount is observed in terms of the decrease in the transmitted lightamount.

In this embodiment, the polarimeter shown in FIG. 3 and explained in thesecond embodiment is used as it is. The principle of measuring the angleof rotation is similar to that for the second embodiment.

Now, a method of measuring the transmitted light amount, i.e., a methodof substantially measuring the scattered light amount will be explained.

While rotating a rotary analyzer 7 is continuously, an output of alock-in amplifier 10 is recorded. Then, the output change of the lock-inamplifier 10 for each predetermined rotational angle of the rotaryanalyzer 7 can be detected. This output change amount corresponds to thetransmitted light amount. This output change amount is standardized bythe measurement value obtained for pure water thereby to determine thescattered light amount in urine.

This method can determine the angle of rotation and the scattered lightamount at the same time in a single measurement process, and it is thuspossible to determine the concentration of a light-scattering substancesuch as albumin. In other words, the range of concentration of albuminand the like required in advance in the first embodiment can be grasped,and therefore the glucose concentration can also be determined.

As described above, according to this embodiment, the glucoseconcentration and the albumin concentration in the urine can be examinedat the same time with a simple configuration and a single measurement,thereby greatly contributing to practical effects.

Another method available for measuring the amount of the scattered lightis to temporarily fix the rotary analyzer 7 at a predetermined angle andto determine the amount from an associated output value of the lock-inamplifier 10.

A similar effect can of course be obtained by directly detecting thescattered light from the side of the sample cell 6 as in the thirdembodiment.

As described above, according to this invention, it is possible toprovide a urinalysis method which is easy to maintain and manage withoutusing any supplies such as the test paper. The angle of rotationincreases, however, with the decrease in the wavelength of the measuredlight due to the optically rotatory dispersion until the appearance ofan abnormal dispersion. Consequently, although the light of a shorterwavelength can be used more advantageously for high accuracymeasurement, the light having a wavelength of about 500 nm or more ismore desirable for urinalysis. This is by reason of the fact that asobvious from FIG. 8 showing the spectral characteristic of normal urine,the light having a wavelength shorter than 500 nm is absorbedincreasingly by urochrome (a yellow component contained in the urine),sometimes deteriorating the measurement accuracy. For similar reason,the desirable wavelength of the light used for measuring the scatteredlight amount is 500 nm or more due to the absorption of urochrome.

The embodiments described above concern a method of determining theglucose concentration and the albumin concentration in urine byprojecting monochromatic light on the urine and determining the angle ofrotation of the urine or the amount of the light scattered in the urine.The polarimeters used for the urinalysis, however, have the problem of alow reliability and a high cost as described above. In view of this,detailed description will be made below about a polarimeter higher inreliability and lower in cost than the conventional polarimeters and theurinalysis apparatus using such a polarimeter.

<<Embodiment 5>>

A configuration of a polarimeter according to this embodiment is shownin FIG. 9. A light source 21 configured of a 180 W low-pressure sodiumlamp, a band-pass filter, a lens, a slit, etc. for projectingsubstantially parallel light is adapted to project a sodium D ray havinga wavelength of 589.0 nm. Of all the light rays projected from the lightsource 21, a polarizer 22 allows only the component in a specificdirection having a plane of vibration parallel to the transmission axisto pass therethrough. A specimen is held in a cylindrical sample cell 23of glass. The sample cell 23 is arranged in such a position that thesubstantially parallel light projected from the light source 21 andpolarized by being passed through the polarizer 22 enters and passesalong the direction of the central axis thereof. The substantial lightpath length of this sample cell 23 is 300 mm.

A solenoid coil 24 wound around the sample cell 23 applies a magneticfield substantially uniformly to the sample cell 23 and the specimenheld therein in the direction of propagation of the light by the currentfrom the current source 25. Specifically, a current of 1 A applied tothe solenoid coil 24 causes a magnetic field H of 5×10³ A/m. The currentsource 25 can supply a current of -5 A to 5 A to the solenoid coil 24.The analyzer 26 is arranged in such a position as to transmit only thosecomponents of the light transmitted through the sample cell 23 which arepolarized in the direction perpendicular to the page, in other words inorthogonal nicol state with the polarizer 22. A light sensor 27 detectsthe light transmitted through the analyzer 26. A computer 28 issues acommand signal to the current source 25 to record and analyze on outputsignal of the light sensor 27.

The operation of this polarimeter will be explained. The computer 28issues a command signal to the current source 25 so that the currentflowing in the solenoid coil 24 is swept from -5 A to 5 A. The outputsignal of the light sensor 27 produced in the process is shown in FIG.10. In FIG. 10, the abscissa represents a current J flowing in thesolenoid coil 24, and the ordinate represents an output signal(arbitrary value) of the light sensor 27.

The solid line is associated with the case in which the pure waterexhibiting no optical rotatory power is measured as a specimen. In thiscase, since the relative angle between a transmission axis of thepolarizer 22 and a transmission axis of the analyzer 26 is π/2, anextinction point appears, when J=0, i.e., when the magnetic field is notapplied to the pure water constituting the specimen and there occurs norotation of the direction of polarization of the light which otherwisemight be caused by the optical Faraday effect. When J is changed, theoutput signal of the light sensor 27 changes according to equation (13)in a manner similar to the case where the analyzer is rotated in theconventional polarimeter. In the polarimeter in this embodiment,however, J corresponds to β in equation (4).

The dotted line in the drawing shows a cane sugar aqueous solution of20° C. in temperature and 500 mg/dl in concentration as a specimen. Inthis case, the extinction point appears at J=2.4 A. Specifically, thecurve is obtained by translating the curve indicated by the solid linein the drawing horizontally along the abscissa by +2.4 A. This 2.4 Adisplacement of the extinction point is caused by the angle of rotationof the specimen. This polarimeter determines the angle of rotation ofthe specimen from the magnitude of this displacement.

The function of the polarimeter according to this embodiment wasquantitatively confirmed using the aqueous solution of cane sugar. Theangle of rotation a and the specific angle of rotation [α] are given asfollows:

    α=[α]/10000×L×C                    (16)

where

L: distance of propagation=light path length of sample cell [m], and

C: concentration of aqueous solution [mg/dl].

The specific angle of rotation [α] of cane sugar for the light having awavelength of 589 nm is 66.5 degrees for the aqueous solution at 20° C.Therefore, the angle of rotation α for this cane sugar aqueous solutionwhen L=0.3 and C=500 is α≈1 degree from equation (16).

Then, the rotational angle a of the direction of polarization due to theoptical Faraday effect is calculated from equation (13) in the mannermentioned below.

From the characteristics of the solenoid coil 24, the magnetic field His given as 1.2×10⁴ A/m when J=2.4 A. This and Verdet's constant V ofwater shown in Table 2 are substituted into equation (13) to give

    a=1.645×10.sup.-2 ×1.2×10.sup.4 ×0.3

    =59.22 [minutes]≈1°

This confirms that the angle of rotation of the specimen coincides withthe rotational angle due to the optical Faraday effect.

Further, using this polarimeter, the angle of rotation was measured ofthe cane sugar aqueous solution having the concentrations of 250, 750and 1000 mg/dl, respectively, at the temperature of 20° C. The result isshown in FIG. 11. In the figure, the abscissa represents the cane sugarconcentration, and the ordinate represents the current J when anextinction point appears. This is indicative of the fact that the outputsignal of the light sensor can be approximated linearly with respect tothe cane sugar concentration.

The conventional polarimeter measures the displacement of an extinctionpoint, i.e., the angle of rotation of a specimen by rotating an analyzerand reading the angle of the analyzer directly. In the polarimeteraccording to the present embodiment, on the other hand, as describedabove, a magnetic field is applied to the specimen with being swept andthe displacement of the extinction point is read in terms of current.This current value is converted into a magnetic field intensity andfurther into an angle thereby to calculate the angle of rotation of thespecimen.

As described above, according to this embodiment, a magnetic field isapplied to the specimen and swept, thereby eliminating the need of meansfor rotating the analyzer. Consequently, it is possible to realize areliable, compact and inexpensive polarimeter of a very high practicalvalue. In sweeping the magnetic field, the intensity is not necessarilychanged continuously but can be changed discretely. Since thecharacteristic of the output signal of the light sensor changing withthe rotation of the direction of polarization is known as shown inequation (2), the angle of rotation can be calculated by measuring themagnetic field intensity at least two points and by interpolation orextrapolation of the measurements. This process is especially effectivefor shortening the measurement time.

<<Embodiment 6>>

The polarimeter according to this embodiment will be explained withreference to FIG. 12. A light source 31 similar to the one used in thefifth embodiment projects the sodium D ray having a wavelength in 589.0mm. A polarizer 32 allows only the polarized light component in aspecified direction, for example, only those polarized light componentsthat are parallel to the page to transmit. A cylindrical sample cell 33for holding the specimen is made of glass and has a substantial lightpath length of 50 mm.

The analyzer 36 is arranged in such an orthogonal nicol state with thepolarizer 32 that only the polarized light components perpendicular tothe page are transmitted. A light sensor 37 detects the lighttransmitted through the analyzer 36. A computer 38 issues a commandsignal to a current source 35, while recording and analyzing the outputsignal of the light sensor 37. Also, the computer 38 issues a commandsignal to the current source 35 and causes the current flowing in thesolenoid coil 34 to be swept up from -5 A to 5 A. The solenoid coil 34has a structure substantially similar to the one used in the fifthembodiment, and applies a magnetic field H of 5×10³ A/m to the samplecell 33 with a current of 1 A. A signal generator 39 supplies avibration-modulated signal to the current source 35. The current source35 converts the vibration-modulated signal into a vibration-modulatedcurrent signal, and superimposes it on the sweeping current commanded bythe computer 38, then the resulting current obtained is applied to thesolenoid coil 34. In this polarimeter, the 1.3 kHz modulated signal isconverted into a vibration-modulated current signal having an amplitudeof 0.02 A, which is supplied to the solenoid coil 34. The lock-inamplifier 40 phase-sensitively detects the output signal of the lightsensor 37 with reference to the vibration-modulated signal of the signalgenerator 39. The output signal of the lock-in amplifier 40 correspondsto the angular frequency component ω of the output signal of the lightsensor 37 in equation (6), i.e., S shown in equation (7). The extinctionpoint, therefore, corresponds to the time when the value S becomes zero.

The operation of the polarimeter will be explained with reference toFIG. 13. The computer 38 issues a command signal to the current source35, and the current flowing in the solenoid coil 34 is swept from -1.5to 1.5 A. The resulting output signal of the lock-in amplifier 40 isshown. In the drawing, the abscissa represents the current J flowing inthe solenoid coil 34, and the ordinate the output signal (arbitraryvalue) of the lock-in amplifier 40.

In the diagram, the solid line represents the measurement of pure waterhaving no optically rotatory power. The dotted line, on the other hand,indicates the measurement of the cane sugar aqueous solution having aconcentration of 250 mg/dl at 20° C. in temperature as a specimen. Anextinction point appears when J=1.21 A. In other words, a new straightline is obtained by translating the solid line by the length of +1.21 Ain parallel. This is quantitatively confirmed in a similar manner to thefifth embodiment.

The angle of rotation α due to cane sugar is given from equation (9) as

    α=[α]/10000×0.05×250

    ≈0.0831 [degrees]

The rotational angle a of the direction of polarization due to theoptical Faraday affect can be calculated from equation (13) as follows.

From the characteristics of the solenoid coil 4', the magnetic field His given as 6.05×10³ A/m when J=1.21 A. This combines with Verdet'sconstant V of water shown in Table 1 to give

    a=1.645×10.sup.-2 ×6.05×10.sup.4 ×0.05

    ≈4.976 [minutes]≈0.083 [degrees]

From this, it is confirmed that the angle of rotation of the specimencoincides with the rotational angle due to the optical Faraday effect.

Further, the angle of rotation of cane sugar aqueous solutions havingthe concentrations of 50, 100, 150 and 250 mg, respectively, wasmeasured at the temperature of 20° C. using this polarimeter. The resultis shown in FIG. 14. This also substantiates the linearity.

With the conventional polarimeter, the analyzer is rotated, and theangle of the analyzer is directly read when the output signal of thelock-in amplifier, i.e., the value S assumes zero. In the polarimeteraccording to this embodiment, on the other hand, the magnetic field isswept, i.e., the current is swept, and the current value is read whenthe output signal S of the lock-in amplifier 40 becomes zero, and isfurther converted into the angle thereby to measure the angle ofrotation of the specimen.

According to this embodiment, an extinction point exists in the sweepingrange of the magnetic field. However, since the output signal S of thelock-in amplifier 40 changes linearly with respect to the magneticfield, i.e., the current J as shown in FIG. 13 and equation (7), even inthe absence of an extinction point within the sweeping range, the angleof rotation can be calculated by extrapolation. Also, since the relationbetween J and S is linear, continuous sweeping is not necessarilyrequired, and the angle of rotation can be calculated by interpolationor extrapolation from measurements at two or more points in the magneticfield. This enables to shorten a measurement time.

Now, explanation will be made about the case in which the surface of thesample cell through which light is to be transmitted is contaminatedafter repetitive operations over a long time. If this contamination iscaused by an optically inactive substance, it follows that T in equation(1) is substantially reduced. As a result, the position of theextinction point becomes ambiguous for a deteriorated measurementaccuracy. In this case, the rate of change of I with respect to θ inequation (2) and the inclination of S with respect to β in equation (7)are reduced. Therefore, the amount of contamination can be detected fromthese amounts of reduction determined by measuring a reference specimenwith a known T. When this amount of contamination exceeds a specifiedvalue, an instruction to clean or replace the sample cell can be given.In such a case, the reference specimen is not always necessary, but thecontamination can be detected from the measurement of a specimen with aknown minimum value of T.

In the case where the contamination is caused by an optically activesubstance, on the other hand, I in equation (2) and S in equation (7)are translated in parallel in the direction of θ and β, respectively. Asa result, the position of an extinction point, i.e., the angle ofrotation measured is also displaced by the amount of particulartranslation. This amount of translation represents an angle of rotationdue to the contaminating substance and can be simply added to the angleof rotation due to the specimen. Therefore, a reference specimen with aknown angle of rotation is measured and the difference between thismeasurement and the known angle of rotation is calculated, so that themeasurement of the specimen is corrected by the difference. As a result,the error caused by the contamination substance can be compensated for.

As described above, by measuring a reference specimen with a known angleof rotation, the error due to the contamination of the sample cell canbe compensated. As a result, the time length before cleaning orreplacing the sample cell after a long time of repetitive uses can belengthened considerably until the transmittance of the plane oftransmission is reduced to a specified value, thus facilitatingmaintenance and management. Especially in the case where the apparatusis used as a home urine analyzer, the maintenance and management easegreatly contributes to the extension of its application.

A sample cell left without being cleaned long time and having the planeof transmission contaminated was actually injected with pure water as aspecimen, and the angle of rotation of this pure water was measured. Inthe process, an extinction point was presented at J=0.02 A. As a result,the angle of rotation d due to the substance contaminating the plane oftransmission of the sample cell is given from equation (13) and Table 2as

    d=1.645×10.sup.-2 ×10.sup.2 ×0.05

    ≈0.082 [minutes]≈1.4×10.sup.-3 [degrees]

As described above, the error of measurement with a contaminated sampleis comparatively small as compared with the angle of rotation exhibitedby the specimen. Also, in the case of using such a sample cell,correction is made by subtracting d from the measurement. In the casewhere the same sample cell is used repetitively over a long time,therefore, a reference specimen with a known angle of rotation, orespecially, water exhibiting no optically rotatory power is measured,and the resulting measurement is used to correct the measurement of thespecimen thereby making possible highly accurate measurement. Thisoperation can extend the length of time before another cleaning orreplacing of the sample cell until the transmittance of the plane oftransmission is reduced to a specified value.

Since the function of an optical Faraday modulator obtained byapplication of a magnetic field to the sample cell as described aboveeliminates the rotating means as in the fifth embodiment, a compact,inexpensive and highly accurate polarimeter can be realized with asimple configuration .

Also, the polarimeter according to this embodiment permits measurementwith a higher accuracy than that of the fifth embodiment, and thereforemeasurement of the angle of rotation of a solution with a lowconcentration is also possible. Further, the fact that the light pathlength can be shortened contributes to a smaller size of the apparatus.

Then, the urine was analyzed using this polarimeter as described below.This examination used a sample cell having a substantial light pathlength L of 100 mm. First, in order to confirm the performance of thispolarimeter against glucose, an analytical curve was prepared. Purewater at 20° C. was prepared together with glucose aqueous solutions 20,100, 200, 300 and 500 mg/dl in concentration with the pure water as asolvent, then the angle of rotation was measured using these asspecimens. The result is shown by white circles in FIG. 19. The abscissarepresents the glucose concentration and the ordinate represents theangle of rotation as converted from the current flowing in the solenoidcoil 34. The result coincides with that obtained using the specificangle of rotation [α]=50 degrees of the 589 nm light for the 20° C.,glucose aqueous solution and equation (16).

Then, the angle of rotation was measured of the urine which had beendetermined to have a glucose concentration of not more than 50 mg/dlarid a concentration of albumin which is urine protein of not more than10 mg/dl. Further, with this urine as a solvent, glucose solutions,i.e., artificial glycosuria 20, 100, 200, 300 and 500 mg/dl inconcentration were prepared. Then, the angle of rotation of theseartificial glycosuria was measured. The result is shown by black circlesin FIG. 19. The angle of rotation of these artificial glycosuria (blackcircles) is represented by a straight line translated by 1.5×10⁻²degrees from the analytical line and accurately reflects the glucoseconcentrations.

The angle of rotation of this urine was 1.5×10⁻² degrees. This is theresult of simple addition of the angles of rotation due to the glucoseand albumin existing in the urine. The specific angle of rotation [α] ofalbumin in an aqueous solution at 20° C. for the 589 nm light is -60degrees, which is combined with equation (9) to calculate the range ofthe angle of rotation A1 of this urine due to the albumin as follows.

    -60/10000×0.1×10=-6×10.sup.-2 degrees≦A1≦0

From this relation, the range of the angle of rotation G1 due to glucoseis calculated as shown below.

    1.5×10.sup.-2 degrees≦G1≦2.1×10.sup.-2 degrees

Further, from this value G1, the range of the glucose concentration Cgcan be calculated from equation (9) in the manner shown below.

    30 mg/dl≦Cg≦42 mg/dl

This coincides with the result of the analysis made beforehand.

In similar fashion, the angle of rotation was measured of the urinewhich had been decided to have a glucose concentration of 300 mg/dl ormore and an albumin concentration of 10 mg/dl or less by the urinalysisusing the test paper. The result was that the angle of rotation of thisurine was 2.2×10⁻² degrees with the glucose concentration Cg determinedto be in the range described below.

    440 mg/dl≦Cg≦452 mg/dl

This also coincides with the analysis made in advance.

In examining the urine having a normal albumin concentration of about 10mg/dl or less, assume that an abnormal value of the urine glucose levelis set to 300 mg/dl or more and that an abnormality is decided when theangle of rotation is not less than 1.5×10⁻¹ degrees. Then, it followsthat an error of only about 12 mg/dl develops.

As described above, the angle of rotation of urine can be measured todetermine the concentration of glucose, protein, etc. in the urinesimply by placing the urine in the sample cell of the polarimeter andapplying a magnetic field to it. As a result, the polarimeter requiresno supplies and is easy to maintain and manage and high in reliability,thus realizing a compact and inexpensive urinalysis apparatus.

When this polarimeter is used as a urinalysis apparatus, even in thecase where the sample cell is contaminated by the routine urinalysis,the use of the polarimeter under consideration with the urinalysisapparatus makes it is possible to maintain a high measurement accuracyby measuring a reference specimen with a known angle of rotation andcorrecting the measurement of the specimen involved. As a result of thisoperation, the time length before cleaning or replacing the sample cellcan be extended until the transmittance of the plane of transmission isreduced to a specified value. Especially when it is used as a homeurinalysis apparatus, the maintenance and management ease is a greatfactor for promoting the extension of the use thereof the apparatus.

Although the embodiment described above concerns the examination inwhich the albumin concentration of the urine examined is low as comparedwith the glucose concentration thereof, the method mentioned above canalso apply with the same effect to analyzing the albumin concentrationof the urine low in which this glucose concentration is low as comparedwith the albumin concentration.

<<Embodiment 7>>

A polarimeter according to this embodiment will be explained withreference to FIG. 16. In FIG. 16, numerals 31 to 40 designate componentssimilar to the corresponding ones in the sixth embodiment. Nevertheless,the current source 35 converts a modulated signal of 1.3 kHz into avibration-modulated current signal having an amplitude of 0.02 A, andsupplies it to the solenoid coil 33, although the current is not swept.Also, the analyzer rotator 41 rotates the analyzer 36 in response to acommand from the computer 38. In this polarimeter, too, the outputsignal of the lock-in amplifier 40 similarly corresponds to the angularfrequency component ω of the output signal of the light sensor 37 inequation (6), i.e., S in equation (7). Therefore, an extinction point ispresented when this S becomes zero. The computer 38 issues a commandsignal to the analyzer rotator 41 thereby to rotate the analyzer 36.When the angle of the analyzer 46 is plotted along the abscissa, and theoutput signal S of the lock-in amplifier 40 is plotted along theordinate, a straight line similar to that in FIG. 13 is obtained. Theangle of the analyzer 36 when the output signal S of the lock-inamplifier 40 becomes zero corresponds to the angle of rotation of thespecimen.

Using this polarimeter, the angle of rotation of cane sugar aqueoussolutions having concentrations of 50, 100, 150 and 250 mg/dl,respectively, were measured at 20° C. in temperature as in the fifthembodiment. A similar result was obtained as in FIG. 14.

In the conventional polarimeter, the analyzer is rotated whilevibration-modulating the direction of polarization by the opticalFaraday modulator, and the angle of the analyzer associated with thetime when the output signal of the lock-in amplifier, i.e., S is zero isread directly to measure the angle of rotation of the specimen. With thepolarimeter according to this embodiment, on the other hand, a magneticfield is applied to the specimen and vibration-modulated, then, theangle of the analyzer associated with a zero output signal S of thelock-in amplifier is read directly to measure the angle of rotation ofthe specimen. Thus the embodiment under consideration eliminates theoptical Faraday modulator, thereby making it possible to provide acompact, inexpensive polarimeter high in measurement accuracy andreliability. Also, the ease of maintenance and management leads to avery great practical effect of the polarimeter.

As in the sixth embodiment, the relation between the angle of theanalyzer and S can be approximated by a linear expression. Therefore,continuous sweep is not necessarily required, but the angle of rotationcan be calculated by interpolation or extrapolation based on themeasurements at two or more points.

Since polarimeter according to this embodiment, like the polarimeter ofthe sixth embodiment, can make measurement with a higher accuracy thanthe polarimeter of the fifth embodiment, the angle of rotation of asolution lower in concentration can also be measured. Further, the factthat a sample cell shorter in light path length can be used contributesto a reduced size of the apparatus

<<Embodiment 8>>

A polarimeter according to this embodiment will be explained withreference to FIG. 17. In FIG. 17, numerals 31 to 40 designate the samecomponent parts which have the same functions as the corresponding onesin the sixth embodiment. The current source 35, however, sweeps thecurrent supplied to the solenoid coil 33 in response to a command fromthe computer 38. The optical Faraday modulator 42 vibration-modulatesthe direction of polarization of the light with an amplitude of 1.4×10⁻³degrees by a vibration-modulated signal of 1.3 kHz generated by a signalgenerator 39. The lock-in amplifier 40 phase-sensitively detects theoutput signal of the light sensor 37 with reference to thevibration-modulated signal of the signal generator 39. The output signalof the lock-in amplifier 40 corresponds to the angular frequencycomponent ω of the output signal of the light sensor 37 in equation (6),i.e., S shown in equation (7). Therefore, an extinction point developswhen the value S becomes zero.

Now, the operation of this polarimeter will be explained. When thecomputer 38 issues a command signal to a current source, a current Jflowing in the solenoid coil 4 and the output signal (arbitrary value)of the lock-in amplifier 40 were determined, thereby obtaining exactlythe same straight line as in FIG. 13. Like in the fifth embodiment,therefore, it was confirmed that the angle of rotation of the specimencoincides with the rotational angle due to the optical Faraday effect.

After measuring the angle of rotation of cane sugar aqueous solutions50, 100, 150 and 250 mg/dl in concentration at 20° C. in temperature,the same result as in FIG. 14 was obtained . This substantiates thelinearity.

According to this embodiment, like in the fifth embodiment, the outputsignal S of the lock-in amplifier is linearly approximated by themagnetic field, i.e, the current J, therefore continuous sweep is notnecessarily required, but the angle of rotation can be calculated byinterpolation or extrapolation from the measurements at two or morepoints in the magnetic field. This also shortens the measurement time.

As described above, according to this embodiment, the direction ofpolarization is vibration-modulated with a minute amplitude by theoptical Faraday modulator, a magnetic field is applied to the specimen,and the magnetic field is swept, thereby eliminating the means ofrotating the analyzer, and realizing a compact, inexpensive polarimeterof a great practical value high in accuracy and reliability easy tomaintain and manage.

Also, the polarimeter according to this embodiment can measure with ahigher accuracy than that of the fifth embodiment, and therefore canmeasure the angle of rotation of a solution low in concentration. Also,measurement of a specimen with a small light path length thus ispossible, which is another factor contributing to a compact apparatus.Although the optical Faraday modulator is used for modulating thedirection of polarization in this embodiment, a piezoelectric device canbe used in place of the optical Faraday modulator for minute vibratoryrotation with a similar effect.

<<Embodiment 9>>

A polarimeter according to this embodiment will be explained withreference to FIG. 18. In the figure, numerals 32 to 40 designatecomponent parts which are similar and function similarly to thecorresponding parts in the sixth embodiment. Nevertheless, asemiconductor laser light source 43 is used instead of the sodium lightsource. The semiconductor laser light source 43 projects substantiallyparallel light having a wavelength of 830 nm and an intensity of 10 mW.The current source 35 converts a modulated signal at 1.3 kHz generatedby a signal generator 39 into a vibration-modulated signal having anamplitude of 0.02 A, and supplies it to the solenoid coil 44. But thecurrent is not swept unlike in the foregoing embodiment. The lock-inamplifier 34 operates in what is called 2F-mode, and phase-sensitivelydetects the output signal of the light sensor 37 with reference to asignal having a frequency twice that of the modulated signal of thesignal generator 39. Specifically, the lock-in amplifier 34 retrievesthe 2×ω component of equation (6). The computer 38 standardizes theoutput signal of the lock-in amplifier 40 by the output signal of thelock-in amplifier 44 and thus calculates the angle of rotation of thespecimen. The principle of this operation is described below.

The output signal of the lock-in amplifier 44 corresponds to S shown inequation (7). Since this value S has a sole function in the case where βis fixed and the values T, I_(O) and δ are constant as in the presentembodiment, therefore, the angle of rotation α can be uniquelycalculated from S. Actually, however, T is varied due to the differencein transmittance between specimens, the contamination of thetransmission window of the specimen, etc. Also, I_(O) changes withfluctuations of the source light intensity, and therefore, it isimpossible to measure the angle of rotation with high accuracy solelyfrom the value S.

In view of this, the output signal of the lock-in amplifier 44 isutilized. The output signal S' of the lock-in amplifier 44 is given as:

    S'=T×I.sub.O ×δ.sup.2 /2                 (17)

Equation (7) is divided by equation (17) for standardization, then Xshown in equation (18) is obtained.

    X=4/δ×(β-α)                         (18)

Since this X does not contains T and I_(O), the angle of rotation α canbe determined from this relation with high accuracy.

Then, the angle of rotation of glucose aqueous solutions 25, 50, 75 and100 mg/dl in concentration, respectively, were measured at 20° C. intemperature using this polarimeter. The process is described below.

First, pure water is measured as a specimen and the angle of theanalyzer 36 is finely adjusted to reduce X to zero. Since the angle ofrotation α of pure water is zero, it follows that β is adjusted to zero.The specimen was measured under this condition. When the concentrationis plotted along the abscissa and the absolute value of X is plottedalong the ordinate, as shown in FIG. 19, a straight line is obtainedwhich is proportional to a and passes through zero. This indicates thatthe angle of rotation can be measured according to this embodiment. Theadjustment of β to zero in advance is not always necessary since thesole purpose of such an adjustment is to determine the magnitude andsign of the angle of rotation of the specimen intuitively as an aid inmeasurement.

As described above, according to this embodiment, a magnetic field isapplied to the specimen and vibration-modulated, and thevibration-modulated frequency component of the output signal of thelight sensor is standardized to a value twice the vibration-modulatedfrequency thereby realizing a compact and inexpensive polarimeter highin accuracy and reliability for a very high practical effect.

Also, the polarimeter according to this embodiment, unlike thepolarimeter of the fifth embodiment, requires no sweeping of the currentsupplied to the solenoid coil. Consequently, the current can bemodulated by the source frequency by connecting an appropriate resistorin series to the solenoid coil and connecting the series circuitdirectly to a 100 V commercial AC power supply. The current source canthus be realized. Although two lock-in amplifiers are needed in thiscase, since the current source can be considerably simplified, apolarimeter lower in cost thin that of the fifth embodiment may beprovided depending on the cost of the current source and the lock-inamplifier.

According to this invention, the angle of rotation is measured on thebasis of the position of the extinction point, however, a specifiedsingle point such as the brightest point can thus be determined as areference since this also fulfill the relation of equation (2). In sucha case, an optimum point is set taking the linearity and stability ofthe light sensor and the lock-in amplifier into due consideration.

Industrial Applicability

The invention can be realized as a glycosometer of an optically activedetection type for detecting the concentration of aqueous solutions offruit sugar, cane sugar, glucose, etc. Also, the use of the apparatusfor urinalysis, especially for examining the concentration of opticallyactive substances like glucose or protein in urine, is expected toextend widely due to its high reliability, compactness, low cost andother features of high practical value as well as the elimination of thetest paper.

According to this invention, a method of urinalysis is provided which iseasy to maintain and manage without using supplies such as the testpaper.

What is claimed is:
 1. A method of urinalysis in which a concentrationof an optically active substance in urine is determined, the methodcomprising the steps ofmeasuring an angle of rotation of said urine,wherein the angle of rotation is measured in the urine containing asubstance to be measured having an optical rotary power and an opticallyactive substance of a known concentration; and determining the range ofconcentration C (kg/dl) of said substance to be measured using thefollowing equation:

    (A-A.sub.h)/(α×L)<C<(A-A.sub.1)/(α×L)

    A.sub.h =L×a×C.sub.h

    A.sub.1 =L×a×C.sub.1

where A_(h) : angle of rotation (degree) of urine measured measured at amaximum value (kg/dl) of concentration of optically active substance ofa known concentration, A_(l) : angle of rotation (degree) of urinemeasured measured at a minimum value (kg/dl) of concentration ofoptically active substance of a known concentration, C_(h) : maximumvalue (kg/dl) of concentration of optically active substance of a knownconcentration, C₁ : minimum value (kg/dl) of concentration of opticallyactive substance of a known concentration, α: specific angle of rotation(degree/cm·dl/kg) of a substance to be measured, a: specific angle(degree/cm·dl/kg) of rotation of optically active substance of a knownconcentration,and L: measurement light path length (cm).
 2. The methodof urinalysis in accordance with claim 1, wherein the urine containing Nkinds of optically active substance s is subjected to the measurementsof the angle of rotation using the light of at least N kinds ofwavelengths, respectively, to determine the concentrations of opticallyactive substances in said urine, N being more than one.
 3. The method ofurinalysis in accordance with claim 1, wherein the concentration of saidoptically active substance and the concentration of a light scatteringsubstance in said urine are determined by measuring a quantity of lightscattered by said urine in addition to the measurement of the angle ofrotation of said urine.
 4. The method of urinalysis in accordance withclaim 1, wherein said optically active substance is at least oneselected from the group consisting of protein, sugar and L-ascorbicacid.
 5. The method of urinalysis in accordance with claim 1, whereinsaid angle of rotation of the urine is measured with respect to thelight having a wavelength of 500 nm or more.